LTC2641/LTC2642
OPERATION
Power-On Reset
32,768 (LTC2642-16N; 8,192 (LTC2642-14N; or 2,048
(LTC2642-12N.
The LTC2641/LTC2642 include a power-on reset circuit
to ensure that the DAC ouput comes up in a known state.
Clearing the DAC
When V is first applied, the power-on reset circuit sets
DD
⎯
⎯
⎯
A 10ns (minimumN low pulse on the CLR pin asynchro-
nously clears the DAC latch to code zero (LTC2641N or to
midscale (LTC2642N.
the output of the LTC2641 to zero-scale (code 0N. The
LTC2642 powers up to midscale (bipolar zeroN. Depend-
ing on the DAC number of bits, the midscale code is:
APPLICATIONS INFORMATION
Unipolar Configuration
The external amplifier provides a unity-gain buffer. The
LTC2642 can also be used in unipolar configuration by
Figure 2 shows a typical unipolar DAC application for
the LTC2641. Tables 1a, 1b and 1c show the unipolar
binary code tables for 16-bit, 14-bit and 12-bit operation.
tying R and ꢁIV to REF. This provides power-up and
FS
clear to midscale.
V
REF
2.5V
OUT
LT®1019CS8-2.5
IN
5V
0.1μF
4.7μF
Table 1a. 16-Bit Unipolar Binary Code Table
(LTC±641-16)
5V/3V
7
GND
DIGITAL INPUT
BINARY NUMBER
IN DAC LATCH
0.1μF
ANALOG OUTPUT
(V
5V/3V
0.1μF
1
REF
)
OUT
V
DD
MꢀS
LꢀS
–
LTC2641-16
1111 1111 1111 1111 V (65,535/65,536N
UNIPOLAR V
0V TO 2.5V
REF
OUT
1/2 LTC6078
V
6
OUT
+
1000 0000 0000 0000 V (32,768/65,536N = V /2
REF
REF
2
3
4
5
16-BIT DAC
CS
0000 0000 0000 0001 V (1/65,536N
REF
SCLK
DIN
CLR
0000 0000 0000 0000 0V
GND
8
26412 F02
Figure ±. 16-Bit Unipolar Output (LTC±641-16) Unipolar VOUT = 0V to VREF
Table 1b. 14-Bit Unipolar Binary Code Table
(LTC±641-14)
Table 1c. 1±-Bit Unipolar Binary Code Table
(LTC±641-1±)
DIGITAL INPUT
BINARY NUMBER
IN DAC LATCH
DIGITAL INPUT
BINARY NUMBER
IN DAC LATCH
ANALOG OUTPUT
(V
ANALOG OUTPUT
(V
)
)
OUT
OUT
MꢀS
LꢀS
MꢀS
LꢀS
1111 1111 1111 11xx V (16,383/16,384N
1111 1111 1111 xxxx
1000 0000 0000 xxxx
0000 0000 0001 xxxx
V
REF
V
REF
V
REF
(4,095/4,096N
REF
1000 0000 0000 00xx V (8,192/16,384N = V /2
(2,048/4,096N = V /2
REF
REF
REF
0000 0000 0000 01xx V (1/16,384N
(1/4,096N
REF
0000 0000 0000 00xx 0V
0000 0000 0000 xxxx 0V
26412f
12
Linear [ Linear ]
